The present invention relates to an antibacterial/antiviral filtering device for ventilation systems, such as anaesthesia machines or ventilators for intensive care.
Patients receiving respirator care are often susceptible to infection during the ventilation. For this reason, it is important to filter the air coming from the respirator from foreign bacteria, viruses, or the like. Also, it is very important to prevent the contamination of the ventilation system; a valuable solution is described in U.S. Pat. No. 4,360,018.
Moreover, the air coming from the respirator is dry and has a relatively low temperature which would make the lungs dry up; should the air be not humidified before its introduction into the patient.
To achieve a solution for both the above problems, it has been proposed to provide a device in which the volume of the filter container is increased in order to achieve an adequate heat and moisture exchange capacity. For this reason, such a combination of heat/moisture exchanger and bacterial filter will be larger than in the case of a device comprising only a filter with the same filtering capacity. However, a larger volume increases the so called dead volume in the respiratory system of the patient. A larger dead volume in the respiratory system give rise to a greater degree of rebreathing of the patient""s exhalation air, resulting in a larger content of carbon dioxide in the air inhaled.
In document WO-A-93/16749 a filter is described which is provided, in a relatively small volume, with a large exchange surface. However, even this solution does not eliminate a certain dead volume in the ventilation system.
In document WO 98/22172 a method for providing assisted ventilation which avoids hypoxia and hypocapnia is disclosed, in which a predetermined dead space in an assisted ventilation system is provided to the patient. The method may also be used to create normocapnia or moderate hypercapnia without causing hypoxia during assisted ventilation. The device has a proximal terminal and a coaxial filter device. According to the said prior art device separated flow circuits are provided for the air inspired and for the air expired by the patient.
The main object of the present invention is therefore to provide a filtering device in which the problem of the dead volume is completely eliminated, thus allowing a much more operational liability of the ventilation apparatus.
A further object of the invention is to provide a filtering device of the kind above defined, which is able to provide heat and moisture to the airflow directed to the patient""s lungs.
A subject of the present invention is therefore an antibacterial/antiviral filtering device for ventilation systems, such as anesthesia machines or ventilators for intensive care, provided with a hose directed to patient. A breathable gas supplying tube, an exhaustion tube and an antibacterial/antiviral filtering device are connected at one side to the hose and at the other side to the breathable gas supplying tube and to the exhaustion tube. The filtering device also comprises a casing, provided with an inlet connected to the breathable gas supplying tube, and an outlet conduit connected to the hose. The filtering device is further characterized in that the casing comprises at least two chambers having parallel axes, which are defined by means of at least a common wall, and in fluid connection one with the other. A first chamber is in communication with the inlet conduit, and is provided with an antibacterial/antiviral filter. The second chamber is in communication with a conduit connected to the exhaustion tube, and with the conduit. The pressure of the inlet breathable gas is thus normally higher than that of the exhaled gas.